Let me just use this thread to point out how awesome stacking armor Penetration in non-ranked games is. Masteries + runes + Brutalizer gives you around 50 Armorpenetration, enough to hit any champion for full damage that does not buy armor (aka everyone in non-ranked games) . And since even tanks prefer to stack health...

While using this on Caytli I started to wonder if abilities who scale of AD also work with ArPen ? It sure looked like it.